Abductor Pollicis Brevis (APB)

Authors

Affiliations

Nate Yomogida, PT, DPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, PT, DPT

Doctor of Physical Therapy

B.A. in Neuroscience

Figure 1: Intrinsic Muscles of the Hand¹

Palmar muscles of the hand (left)²

Table 1

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Origin

• Flexor retinaculum³
• Scaphoid³
• Trapezium³

Insertion

Lateral side of base of 1st proximal phalanx (via radial seasamoid)³

Innervation

Recurrent Br. of Median N. (C8, T1)³ # Action {#action}

1st CMC: Abduction³

APB Strength Test for Carpal Tunnel Syndrome

“The patient is positioned in sitting with their hand supported by the clinician. The clinician asked the patient to touch the pads of the thumb and small finger together. After asking the patient to keep the pads of the thumb and small finger together, the clinician applies a strong force in order to resist thumb abduction (Fig. 18-63). A positive test is a weakness in some abduction with resisted testing as compared to the other hand. Studies performed to determine weakness in the APB are relatively consistent, demonstrating moderate diagnostic accuracy.”⁴

Notes

1.

Betts JG, Blaker W. Openstax Anatomy and Physiology. 2nd ed. OpenStax; 2022. https://openstax.org/details/books/anatomy-and-physiology-2e/?Book%20details

2.

Gray H. Anatomy of the Human Body. 20th ed. (Lewis WH, ed.). Lea & Febiger; 1918. https://www.bartleby.com/107/

3.

Gilroy AM, MacPherson BR, Wikenheiser JC, Voll MM, Wesker K, Schünke M, eds. Atlas of Anatomy. 4th ed. Thieme; 2020.

4.

Dutton M. Dutton’s Orthopaedic Examination, Evaluation, and Intervention. 5th ed. McGraw Hill Education; 2020.